Publications
788 results found
Gervasio S, Voigt M, Kersting UG, et al., 2017, Sensory Feedback in Interlimb Coordination: Contralateral Afferent Contribution to the Short-Latency Crossed Response during Human Walking., PLoS One, Vol: 12
A constant coordination between the left and right leg is required to maintain stability during human locomotion, especially in a variable environment. The neural mechanisms underlying this interlimb coordination are not yet known. In animals, interneurons located within the spinal cord allow direct communication between the two sides without the need for the involvement of higher centers. These may also exist in humans since sensory feedback elicited by tibial nerve stimulation on one side (ipsilateral) can affect the muscles activation in the opposite side (contralateral), provoking short-latency crossed responses (SLCRs). The current study investigated whether contralateral afferent feedback contributes to the mechanism controlling the SLCR in human gastrocnemius muscle. Surface electromyogram, kinematic and kinetic data were recorded from subjects during normal walking and hybrid walking (with the legs moving in opposite directions). An inverse dynamics model was applied to estimate the gastrocnemius muscle proprioceptors' firing rate. During normal walking, a significant correlation was observed between the magnitude of SLCRs and the estimated muscle spindle secondary afferent activity (P = 0.04). Moreover, estimated spindle secondary afferent and Golgi tendon organ activity were significantly different (P ≤ 0.01) when opposite responses have been observed, that is during normal (facilitation) and hybrid walking (inhibition) conditions. Contralateral sensory feedback, specifically spindle secondary afferents, likely plays a significant role in generating the SLCR. This observation has important implications for our understanding of what future research should be focusing on to optimize locomotor recovery in patient populations.
Úbeda A, Sartori M, Del-Ama AJ, et al., 2017, Decoding Muscle Excitation Primitives from Slow Cortical Potentials During Knee Flexion-Extension, Biosystems and Biorobotics, Pages: 1151-1156
Linear decoders have been successfully applied to extract human limbs kinematics from low-frequency cortical modulations. In this, intermediate descending motor pathways are absorbed in the regression. Here we propose the use of linear decoders to map cortical function to the spinal function (muscle primitive-level), thus shortening the transmission distance and reducing the dimensionality of the decoding of a large number of muscles. Our first results show that it is possible to accurately reconstruct muscle primitives computed from knee flexion-extension and to successfully detect muscle activity during repetitive cyclic movements.
Xiong X, Sartori M, Dosen S, et al., 2017, A novel controller for bipedal locomotion integrating feed-forward and feedback mechanisms, Biosystems and Biorobotics, Pages: 285-289
It has been recognized that bipedal locomotion is controlled using feed-forward (e.g., patterned) and feedback (e.g., reflex) control schemes. However, most current controllers fail to integrate the two schemes to simplify speed control of bipedal locomotion. To solve this problem, we here propose a patterned muscle-reflex controller integrating feed-forward control with a muscle-reflex controller. In feed-forward control, the pattern generator is modeled as a Matsuoka neural oscillator that produces four basic activation patterns that mimic those extracted experimentally via electromyograms (EMGs). The associated weights of the patterns for 16 Hill-type musculotendon units (MTUs) are calculated based on a predictive model of muscle excitations under human locomotion. The weighted sums of the basic activation patterns serve as the pre-stimulations to muscle-reflex control of the Hill-type MTUs actuating a 2D-simulated biped. As a result, the proposed controller enables the biped to easily regulate its speed on an even ground by only adjusting the descending input. The speed regulation does not require re-optimizations of the controller for various walking speeds, compared to pure muscle-reflex controllers.
Marković M, Engels LF, Schweisfurth M, et al., 2017, Does sensory feedback in prosthetic hands provide functional benefits in daily activities of amputees?, Biosystems and Biorobotics, Pages: 589-593
In an attempt to investigate the value of artificial somatosensory feedback in upper limb prostheses we designed a novel, modular feedback system and paired it with a battery of clinically-relevant tests. Three transhumeral amputee subjects, wearing dexterous myoelectric hands, participated in the study. The obtained objective as well as subjective performance outcomes indicate that the benefits of feedback might be seen only in dexterous, delicate tasks.
Isaković M, Štrbac M, Belić M, et al., 2017, Dynamic stimulation patterns for conveying proprioceptive information from multi-dof prosthesis, Biosystems and Biorobotics, Pages: 601-605
The aim of this study was to investigate the ability of the amputees to understand and identify proprioceptive feedback information presented by a set of dynamic stimulation patterns. The feedback relied on spatial coding of electrotactile stimuli, provided by a multichannel electrical stimulator, over custom designed array electrodes. Four stimulation patterns representing opening, closing, pronation and supination of a prosthetic hand were defined to mimic the change of the corresponding prosthesis degree of freedom. The psychometric evaluation on three amputee subjects confirmed that the four proposed dynamic stimulation patterns can be distinguished successfully after a short training.
Ubeda A, Del Vecchio A, Sartori M, et al., 2017, Corticospinal coherence during frequency-modulated isometric ankle dorsiflexion, Converging Clinical and Engineering Research on Neurorehabilitation II, Editors: Ibanez, GonzalezVargas, Azorin, Akay, Pons, Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 135-140, ISBN: 978-3-319-46668-2
In this paper we analyze the role of corticomuscular transmission for the time-varying force control. Corticospinal coherence is assessed during frequency-modulated isometric ankle dorsiflexions. Our preliminary results show a significant coupling between EEG signals and motor unit spike trains at the target frequency, suggesting that low-frequency cortical oscillations may have an important functional role in force control.
Sartori M, Durandau G, Farina D, 2017, Neuromusculoskeletal Models of Human-Machine Interaction in Individuals Wearing Lower Limb Assistive Technologies, Biosystems and Biorobotics, Pages: 827-831
This abstract outlines how musculoskeletal modeling formulations driven by electrophysiological recordings can be used to understand the complex dynamics of human-machine interaction in healthy and impaired individuals wearing lower limb orthoses. We investigate two scenarios. The first involves a healthy individual walking with a powered exoskeleton. The second involves an impaired individual walking with a passive knee-ankle-foot orthosis. We demonstrate how offline and online modeling can be used for predicting the individual’s neuromusculoskeletal responses to the devices connected in parallels to their limbs.
Yavuz US, Negro F, Diedrichs R, et al., 2017, Reflex circuitry originating from the muscle spindles to the tibialis anterior muscle, Biosystems and Biorobotics, Pages: 177-181
In this study we investigated whether the reflex excitatory and inhibitory inputs to motor neuron pools are uniformly or differentially distributed. We found that the distribution of monosynaptic excitatory (H-reflex) and reciprocal inhibitory inputs to different size motor neurons fitted gamma distributions with different skew values. This result can be interpreted as due to a differential distribution of afferent inputs on motor neurons.
Schweisfurth MA, Bentz T, Došen S, et al., 2017, TMR Improves Performance of Compensatory Tracking Using Myoelectric Control, Biosystems and Biorobotics, Pages: 661-666
We explored the performance of a glenohumeral TMR (targeted muscle reinnervation) patient in controlling the activity of two reinnervated muscles of the chest and back during a compensatory tracking task that implied quick switches of activity between the two muscles. The same task was conducted in intact-bodied subjects, using either the wrist flexor/extensor muscles (innervated by the nerves were used as donors in the TMR patient) or the chest/back muscles that were re-innervated in the patient following the TMR. As expected, the intact-bodied subjects showed better control performance when using the wrist muscles than when using the chest and back muscles. Using the reinnervated chest and back muscles, the TMR patient performed similarly in the compensatory task than the able-bodied subjects when they used wrist muscles and his performance was superior than that of the able-bodied subjects using their chest and back muscles for control. These results indicate that the control properties have been improved through TMR.
Gallego JA, Dideriksen JL, Holobar A, et al., 2017, Neural Control of Muscles in Tremor Patients, Biosystems and Biorobotics, Pages: 129-134
Essential tremor and Parkinson’s disease cause abnormal oscillatory activity in a variety of brain structures that is transmitted to spinal motoneurons and generates tremor. Because the motoneuron pool integrates synaptic inputs from descending and spinal circuits, the decoding of its activity provides a view on all the neural pathways involved in tremor generation. We investigated tremor mechanisms by analyzing the behavior of populations of motoneurons within a single muscle, across antagonist muscle pairs, and in relation to cortical activity. We observed that tremor is caused by a common cortical input projected to all motoneurons. We also found that spinal reflex pathways contribute fundamentally to shaping tremor properties. We posit that although ET and PD tremor are centrally generated, tremor properties are strongly determined by the interaction between descending and afferent inputs to the motoneuron pool.
Sartori M, Yavuz US, Frömmel C, et al., 2017, From spiking motor units to joint function, Biosystems and Biorobotics, Pages: 1275-1279
This abstract proposes a modeling methodology that enables reconstructing ankle joint mechanical function from muscle motor unit spike trains decomposed from high-density electromyography signals. The abstract outlines methods and results and discusses the implication that this approach can have for enhancing our understanding of the neuro-mechanical processes underlying human movement.
Sartori M, Rubenson J, Lloyd DG, et al., 2017, Subject-Specificity via 3D Ultrasound and Personalized Musculoskeletal Modeling, Biosystems and Biorobotics, Pages: 639-642
This study combines experimental-based and model-based methodologies for accessing in vivo musculoskeletal function in healthy individuals. We use ultrasound and dynamometer technologies to derive subject-specific muscle parameters including muscle isometric force, optimal fiber length and tendon slack length. We then assess the impact of subject-specificity on the electromyography-driven simulation of walking of the composite musculoskeletal system.
Sartori M, González-Vargas J, Došen S, et al., 2017, Predictive framework of human locomotion based on neuromuscular primitives and modeling, Biosystems and Biorobotics, Pages: 265-269
Synthesizing human movement in computational neuro-mechanical models is a complex problem. In this study, we describe a predictive framework that combines computational models of neural, sensory and mechanical processes. Our proposed formulation facilitates the transition towards the design of a new class of bio-mimetic assistive devices that do not rely on explicit representations of task-specific motor control models.
Mrachacz-Kersting N, Stevenson AJT, Aliakbaryhosseinabadi S, et al., 2017, An Associative Brain-Computer-Interface for Acute Stroke Patients, Biosystems and Biorobotics, Pages: 841-845
An efficient innovative Brain-Computer-Interface system that empowers chronic stroke patients to control an artificial activation of their lower limb muscle through task specific motor intent has been tested in the past. In the current study it was applied to acute stroke patients. The system consists in detecting the movement-related cortical potential (MRCP) using scalp electrodes as the patient attempts to perform a dorsiflexion task. This is translated into the control command for an electrical stimulator to generate a stimulus to the nerve that innervates and thus activates the prime mover (tibialis anterior). This activation is precisely and individually timed such that the sensory signal arising from the stimulation reaches the motor cortex during its maximum activation due to the intention. The output of the motor cortical area representing the dorsiflexor muscles was significantly enhanced in all patients tested following a single session of 30 repetitions. All patients were able to perform the intervention with minimal training and very few repetitions, making this a feasible new efficient approach for restoration of motor function in stroke patients. Such few necessary applications of the protocol make it a unique approach in comparison to available techniques and paves the way for at home use devices.
Aliakbaryhosseinabadi S, Kostic V, Pavlovic A, et al., 2017, Effect of Attention Variation in Stroke Patients: Analysis of Single Trial Movement-Related Cortical Potentials, Biosystems and Biorobotics, Pages: 983-987
We have previously developed a Brain-computer interface (BCI) for neuromodulation based on movement related cortical potentials (MRCP). Since successful induction of plasticity is dependent on the attention of the user, the aim of this study was to analyze the changes in MRCPs during imposed attentional shifts in patients. We recorded EEG signals from Cz and its surrounding channels in seven chronic stroke patients, who were asked to attempt ankle dorsiflexion in two subsets of 30 repetitions. Each subset was separated from the other by an auditory oddball task comprised of three tones. Patients were asked to detect the target tone by pressing a button. Nine temporal features were extracted from single trial MRCPs and compared between the two subsets of dorsiflexion that were interspersed by the oddball task. The amplitude of the MRCP negativity, pre-movement slopes, pre-movement variability and movement detection latency and accuracy changed significantly when attention was diverted from the main task of dorsiflexion. This has significant implications for BCIs designed to induce plasticity since detection failure will result in inappropriate device control.
Vujaklija I, Amsuess S, Roche AD, et al., 2017, Clinical Evaluation of a Socket-Ready Naturally Controlled Multichannel Upper Limb Prosthetic System, 2nd International Symposium on Wearable Robotics (WeRob), Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 3-7, ISSN: 2195-3562
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- Citations: 7
Vujaklija I, Muceli S, Bergmeister K, et al., 2017, Prospects of Neurorehabilitation Technologies Based on Robust Decoding of the Neural Drive to Muscles Following Targeted Muscle Reinnervation, 3rd International Conference on NeuroRehabilitation (ICNR), Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 1359-1363, ISSN: 2195-3562
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- Citations: 1
Muceli S, Vujaklija I, Jiang N, et al., 2017, A Biologically-Inspired Robust Control System for Myoelectric Control, 3rd International Conference on NeuroRehabilitation (ICNR), Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: 975-979, ISSN: 2195-3562
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- Citations: 4
Yao L, Xie T, Wu Z, et al., 2017, Towards Online Functional Brain Mapping and Monitoring During Awake Craniotomy Surgery Using ECoG-Based Brain-Surgeon Interface (BSI), BRAIN-COMPUTER INTERFACE RESEARCH: A STATE-OF-THE-ART SUMMARY 6, Editors: Guger, Allison, Lebedev, Publisher: SPRINGER-VERLAG BERLIN, Pages: 91-96, ISBN: 978-3-319-64372-4
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Sartori M, Fernandez JW, Modenese L, et al., 2016, Toward modeling locomotion using electromyography-informed 3D models: application to cerebral palsy, WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE, Vol: 9, ISSN: 1939-5094
This position paper proposes a modeling pipeline to develop clinically relevant neuromusculoskeletal models to understand and treat complex neurological disorders. Although applicable to a variety of neurological conditions, we provide direct pipeline applicative examples in the context of cerebral palsy (CP). This paper highlights technologies in: (1) patient-specific segmental rigid body models developed from magnetic resonance imaging for use in inverse kinematics and inverse dynamics pipelines; (2) efficient population-based approaches to derive skeletal models and muscle origins/insertions that are useful for population statistics and consistent creation of continuum models; (3) continuum muscle descriptions to account for complex muscle architecture including spatially varying material properties with muscle wrapping; (4) muscle and tendon properties specific to CP; and (5) neural-based electromyography-informed methods for muscle force prediction. This represents a novel modeling pipeline that couples for the first time electromyography extracted features of disrupted neuromuscular behavior with advanced numerical methods for modeling CP-specific musculoskeletal morphology and function. The translation of such pipeline to the clinical level will provide a new class of biomarkers that objectively describe the neuromusculoskeletal determinants of pathological locomotion and complement current clinical assessment techniques, which often rely on subjective judgment.
Marateb HR, Farahi M, Rojas M, et al., 2016, Detection of multiple innervation zones from multi-channel surface emg recordings with low signal-to-noise ratio using graph-cut segmentation, PLOS One, Vol: 11, ISSN: 1932-6203
Knowledge of the location of muscle Innervation Zones (IZs) is important in many applications, e.g. for minimizing the quantity of injected botulinum toxin for the treatment of spasticity or for deciding on the type of episiotomy during child delivery. Surface EMG (sEMG) can be noninvasively recorded to assess physiological and morphological characteristics of contracting muscles. However, it is not often possible to record signals of high quality. Moreover, muscles could have multiple IZs, which should all be identified. We designed a fully-automatic algorithm based on the enhanced image Graph-Cut segmentation and morphological image processing methods to identify up to five IZs in 60-ms intervals of very-low to moderate quality sEMG signal detected with multi-channel electrodes (20 bipolar channels with Inter Electrode Distance (IED) of 5 mm). An anisotropic multilayered cylinder model was used to simulate 750 sEMG signals with signal-to-noise ratio ranging from -5 to 15 dB (using Gaussian noise) and in each 60-ms signal frame, 1 to 5 IZs were included. The micro- and macro- averaged performance indices were then reported for the proposed IZ detection algorithm. In the micro-averaging procedure, the number of True Positives, False Positives and False Negatives in each frame were summed up to generate cumulative measures. In the macro-averaging, on the other hand, precision and recall were calculated for each frame and their averages are used to determine F1-score. Overall, the micro (macro)-averaged sensitivity, precision and F1-score of the algorithm for IZ channel identification were 82.7% (87.5%), 92.9% (94.0%) and 87.5% (90.6%), respectively. For the correctly identified IZ locations, the average bias error was of 0.02±0.10 IED ratio. Also, the average absolute conduction velocity estimation error was 0.41±0.40 m/s for such frames. The sensitivity analysis including increasing IED and reducing interpolation coefficient for time samples was perfor
Aliakbaryhosseinabadi S, Kostic V, Pavlovic A, et al., 2016, Influence of attention alternation on movement-related cortical potentials in healthy individuals and stroke patients., Clinical Neurophysiology, Vol: 128, Pages: 165-175, ISSN: 1872-8952
OBJECTIVE: In this study, we analyzed the influence of artificially imposed attention variations using the auditory oddball paradigm on the cortical activity associated to motor preparation/execution. METHODS: EEG signals from Cz and its surrounding channels were recorded during three sets of ankle dorsiflexion movements. Each set was interspersed with either a complex or a simple auditory oddball task for healthy participants and a complex auditory oddball task for stroke patients. RESULTS: The amplitude of the movement-related cortical potentials (MRCPs) decreased with the complex oddball paradigm, while MRCP variability increased. Both oddball paradigms increased the detection latency significantly (p<0.05) and the complex paradigm decreased the true positive rate (TPR) (p=0.04). In patients, the negativity of the MRCP decreased while pre-phase variability increased, and the detection latency and accuracy deteriorated with attention diversion. CONCLUSION: Attention diversion has a significant influence on MRCP features and detection parameters, although these changes were counteracted by the application of the laplacian method. SIGNIFICANCE: Brain-computer interfaces for neuromodulation that use the MRCP as the control signal are robust to changes in attention. However, attention must be monitored since it plays a key role in plasticity induction. Here we demonstrate that this can be achieved using the single channel Cz.
Stango A, Yazdandoost KY, Negro F, et al., 2016, Characterization of in-body to on-body wireless radio frequency link for upper limb prostheses., PLOS One, Vol: 11, ISSN: 1932-6203
Wireless implanted devices can be used to interface patients with disabilities with the aim of restoring impaired motor functions. Implanted devices that record and transmit electromyographic (EMG) signals have been applied for the control of active prostheses. This simulation study investigates the propagation losses and the absorption rate of a wireless radio frequency link for in-to-on body communication in the medical implant communication service (MICS) frequency band to control myoelectric upper limb prostheses. The implanted antenna is selected and a suitable external antenna is designed. The characterization of both antennas is done by numerical simulations. A heterogeneous 3D body model and a 3D electromagnetic solver have been used to model the path loss and to characterize the specific absorption rate (SAR). The path loss parameters were extracted and the SAR was characterized, verifying the compliance with the guideline limits. The path loss model has been also used for a preliminary link budget analysis to determine the feasibility of such system compliant with the IEEE 802.15.6 standard. The resulting link margin of 11 dB confirms the feasibility of the system proposed.
Franceschi M, Seminara L, Dosen S, et al., 2016, A system for electrotactile feedback using electronic skin and flexible matrix electrodes: Experimental evaluation, IEEE Transactions on Haptics, Vol: 10, Pages: 162-172, ISSN: 1939-1412
Myoelectric prostheses are successfully controlled using muscle electrical activity, thereby restoring lost motor functions. However, the somatosensory feedback from the prosthesis to the user is still missing. The sensory substitution methods described in the literature comprise mostly simple position and force sensors combined with discrete stimulation units. The present study describes a novel system for sophisticated electrotactile feedback integrating advanced distributed sensing (electronic skin) and stimulation (matrix electrodes). The system was tested in eight healthy subjects who were asked to recognize the shape, trajectory, and direction of a set of dynamic movement patterns (single lines, geometrical objects, letters) presented on the electronic skin. The experiments demonstrated that the system successfully translated the mechanical interaction into the moving electrotactile profiles, which the subjects could recognize with a good performance (shape recognition: 86±8% lines, 73±13% geometries, 72±12% letters). In particular, the subjects could identify the movement direction with a high confidence. These results are in accordance with previous studies investigating the recognition of moving stimuli in human subjects. This is an important development towards closed-loop prostheses providing comprehensive and sophisticated tactile feedback to the user, facilitating the control and the embodiment of the artificial device into the user body scheme.
Castronovo AM, Mrachacz-Kersting N, Landi F, et al., 2016, Motor Unit Coherence at Low Frequencies Increases Together with Cortical Excitability Following a Brain-Computer Interface Intervention in Acute Stroke Patients., 3rd International Conference on NeuroRehabilitation (ICNR2016), Publisher: Springer, Pages: 1001-1005
This study aims at investigating the neurophysiological correlates of increased cortical excitability following a Brain-Computer interface based intervention in three acute stroke survivors. The analysis was performed on high-density EMG signals recorded from the Tibialis Anterior muscle. All patients showed an increased excitability in the motor cortex area of interest following the BCI intervention. Moreover, coherence between motor unit spike trains increased in the frequency band 1–5 Hz, suggesting an increase in the common oscillatory drive to the target muscle.
Clemente F, Dosen S, Lonini L, et al., 2016, Humans Can Integrate Augmented Reality Feedback in Their Sensorimotor Control of a Robotic Hand, IEEE Transactions on Human-Machine Systems, Vol: 47, Pages: 583-589, ISSN: 2168-2291
Tactile feedback is pivotal for grasping and manipulation inhumans. Providing functionally effective sensory feedback to prosthesesusers is an open challenge. Past paradigms were mostly based on vibroorelectrotactile stimulations. However, the tactile sensitivity on the targetedbody parts (usually the forearm) is greatly less than that of thehand/fingertips, restricting the amount of information that can be providedthrough this channel. Visual feedback is the most investigated techniquein motor learning studies, where it showed positive effects in learning bothsimple and complex tasks; however, it was not exploited in prosthetics dueto technological limitations. Here, we investigated if visual information providedin the form of augmented reality (AR) feedback can be integratedby able-bodied participants in their sensorimotor control of a pick-and-lifttask while controlling a robotic hand. For this purpose, we provided visualcontinuous feedback related to grip force and hand closure to the participants.Each variable was mapped to the length of one of the two ellipseaxes visualized on the screen of wearable single-eye display AR glasses.We observed changes in behavior when subtle (i.e., not announced to theparticipants) manipulation of the AR feedback was introduced, which indicatedthat the participants integrated the artificial feedback within thesensorimotor control of the task. These results demonstrate that it is possibleto deliver effective information through AR feedback in a compact andwearable fashion. This feedback modality may be exploited for deliveringsensory feedback to amputees in a clinical scenario.
Aszmann OC, Vujaklija I, Roche AD, et al., 2016, Elective amputation and bionic substitution restore functional hand use after critical soft tissue injuries, Scientific Reports, Vol: 6, ISSN: 2045-2322
Critical soft tissue injuries may lead to a non-functional and insensate limb. In these cases standard reconstructive techniques will not suffice to provide a useful outcome, and solutions outside the biological arena must be considered and offered to these patients. We propose a concept which, after all reconstructive options have been exhausted, involves an elective amputation along with a bionic substitution, implementing an actuated prosthetic hand via a structured tech-neuro-rehabilitation program. Here, three patients are presented in whom this concept has been successfully applied after mutilating hand injuries. Clinical tests conducted before, during and after the procedure, evaluating both functional and psychometric parameters, document the benefits of this approach. Additionally, in one of the patients, we show the possibility of implementing a highly functional and natural control of an advanced prosthesis providing both proportional and simultaneous movements of the wrist and hand for completing tasks of daily living with substantially less compensatory movements compared to the traditional systems. It is concluded that the proposed procedure is a viable solution for re-gaining highly functional hand use following critical soft tissue injuries when existing surgical measures fail. Our results are clinically applicable and can be extended to institutions with similar resources.
Patel GK, Dosen S, Castellini C, et al., 2016, Multichannel electrotactile feedback for simultaneous and proportional myoelectric control, Journal of Neural Engineering, Vol: 13, ISSN: 1741-2560
© 2016 IOP Publishing Ltd. Objective. Closing the loop in myoelectric prostheses by providing artificial somatosensory feedback to the user is an important need for prosthetic users. Previous studies investigated feedback strategies in combination with the control of one degree of freedom of simple grippers. Modern hands, however, are sophisticated multifunction systems. In this study, we assessed multichannel electrotactile feedback integrated with an advanced method for the simultaneous and proportional control of individual fingers of a dexterous hand. Approach. The feedback used spatial and frequency coding to provide information on the finger positions (normalized flexion angles). A comprehensive set of conditions have been investigated in 28 able-bodied subjects, including feedback modalities (visual, electrotactile and no feedback), control tasks (fingers and grasps), systems (virtual and real hand), control methods (ideal and realistic) and range of motion (low and high). The task for the subjects was to operate the hand using closed-loop myoelectric control and generate the desired movement (e.g., selected finger or grasp at a specific level of closure). Main results. The subjects could perceive the multichannel and multivariable electrotactile feedback and effectively exploit it to improve the control performance with respect to open-loop grasping. The improvement however depended on the reliability of the feedforward control, with less consistent control exhibiting performance trends that were more complex across the conditions. Significance. The results are promising for the potential application of advanced feedback to close the control loop in sophisticated prosthetic systems.
Torricelli D, Gonzalez J, Weckx M, et al., 2016, Human-like compliant locomotion: state of the art of robotic implementations, Bioinspiration and Biomimetics, Vol: 11, ISSN: 1748-3182
This review paper provides a synthetic yet critical overview of the key biomechanical principles of human bipedal walking and their current implementation in robotic platforms. We describe the functional role of human joints, addressing in particular the relevance of the compliant properties of the different degrees of freedom throughout the gait cycle. We focused on three basic functional units involved in locomotion, i.e. the ankle-foot complex, the knee, and the hip-pelvis complex, and their relevance to whole-body performance. We present an extensive review of the current implementations of these mechanisms into robotic platforms, discussing their potentialities and limitations from the functional and energetic perspectives. We specifically targeted humanoid robots, but also revised evidence from the field of lower-limb prosthetics, which presents innovative solutions still unexploited in the current humanoids. Finally, we identified the main critical aspects of the process of translating human principles into actual machines, providing a number of relevant challenges that should be addressed in future research.
Schweisfurth MA, Markovic M, Dosen S, et al., 2016, Electrotactile EMG feedback improves the control of prosthesis grasping force, Journal of Neural Engineering, Vol: 13, ISSN: 1741-2560
© 2016 IOP Publishing Ltd. Objective. A drawback of active prostheses is that they detach the subject from the produced forces, thereby preventing direct mechanical feedback. This can be compensated by providing somatosensory feedback to the user through mechanical or electrical stimulation, which in turn may improve the utility, sense of embodiment, and thereby increase the acceptance rate. Approach. In this study, we compared a novel approach to closing the loop, namely EMG feedback (emgFB), to classic force feedback (forceFB), using electrotactile interface in a realistic task setup. Eleven intact-bodied subjects and one transradial amputee performed a routine grasping task while receiving emgFB or forceFB. The two feedback types were delivered through the same electrotactile interface, using a mixed spatial/frequency coding to transmit 8 discrete levels of the feedback variable. In emgFB, the stimulation transmitted the amplitude of the processed myoelectric signal generated by the subject (prosthesis input), and in forceFB the generated grasping force (prosthesis output). The task comprised 150 trials of routine grasping at six forces, randomly presented in blocks of five trials (same force). Interquartile range and changes in the absolute error (AE) distribution (magnitude and dispersion) with respect to the target level were used to assess precision and overall performance, respectively. Main results. Relative to forceFB, emgFB significantly improved the precision of myoelectric commands (min/max of the significant levels) for 23%/36% as well as the precision of force control for 12%/32%, in intact-bodied subjects. Also, the magnitude and dispersion of the AE distribution were reduced. The results were similar in the amputee, showing considerable improvements. Significance. Using emgFB, the subjects therefore decreased the uncertainty of the forward pathway. Since there is a correspondence between the EMG and force, where the former anticipates the latte
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